1. Field of the Invention
This invention relates to a rapid curable method for preparing a polyisocyanurate composite which is highly rigid and excellent in heat resistance.
2. Related Background Art
In the art of fiber reinforced plastics (FRP) molding technique, the method of obtaining a FRP by injecting a thermosetting resin reaction liquid such as unsaturated polyester resin, vinyl ester resin, epoxy resin, etc. into a mold in which a fibrous reinforcing material is previously set has been generally called the resin injection method or the resin transfer molding method and known as the method with good economical efficiency utilizing in-mold polymerization.
In industrial fields, particularly the field of automotive industry, it has been demanded to manufacture structural materials having heat resistance in short molding cycle time. However, in the above method, no material satisfactory in both aspects of rapid curability and heat resistance has been obtained.
On the other hand, in the field of polyurethane elastomer, the reaction injection molding (hereinafter called RIM) technique has been well developed and applied particularly to molding of bumper, facia, etc. of automobile. Since this technique is suitable for manufacturing large size molding, specific features reside in that integration of a large number of parts is possible, and also that the molding cycle time is by far shorter as compared with the above resin injection method.
In recent years, it has been attempted to obtain a composite of thermosetting resin by means of rapid curing by combining the RIM technique with the resin injection method.
More specifically, it is a method in which a fibrous reinforcing material is previously set in a mold, and a thermosetting resin reaction liquid is injected by a RIM machine into the mold.
However, with the reaction liquid for RIM of the prior art, particularly in the case of polyurethane, the reaction begins simultaneously with mixing to cause increase in viscosity, whereby there is the problem that penetrability into the fibrous reinforcing material is inferior. Also, other RIM systems have been investigated, but no material satisfactory in such points as penetrability, rapid curability, high rigidity, heat resistance, etc. has been obtained.
The present inventors have intensively studied in order to obtain a composite having high rigidity and heat resistance in short molding cycle time by rapid curing, and consequently accomplished the present invention.